The present invention relates to an electromagnetically interference-proof flight control device having a hydraulic positioning drive also called hydraulic actuator for a control surface, the position of which can be adjusted.
Such a device is known from the company brochure of the firm Bertea Corp., Irvine, Calif., with the title "Hydra-Optic Servo Control Demonstrator". There, a control device for aircraft is presented which is completely shielded from external electromagnetic interference. The control signals are fed in optically, and more specifically via light guides. The power for actuating the positioning drive for the control surface to be adjusted is supplied via a hydraulic pressure line with which a hydraulic return line is associated. This flight control device is characterized by the feature that there are no electric leads of any kind which could be subjected to electromagnetic interference. The device is connected to the outside world only via light guides as well as hydraulic lines. In the interior of the device, the optical control signals are converted in an opto-electronic converter into corresponding drive signals for an electrohydraulic valve arrangement which precedes the positioning drive and serves to supply the latter with hydraulic energy in the manner determined by the control signals, to thereby bring about the desired setting of the control surface. The power required for the opto-electronic signal conversion as well as for driving the electrohydraulic valve arrangement is made available by a hydraulic motor which is fed from the hydraulic pressure line in parallel with the mentioned valve arrangement.
It must be viewed as a disadvantage of the known flight control device that a hydraulic motor is used for the internal power supply. While it is avoided thereby that electric energy must be fed in from the outside as is known, for instance, from EP-Al 0 046 875 (see FIG. 7), whereby electromagnetic interference can penetrate, such a hydraulic motor has moving parts and is therefore interference-prone as well as wear-prone and consequently requires a certain amount of maintenance.